Mice for conditional hnRNPLL expression or deletion were generated. HnRNPLL cDNA was knocked into the ROSA26 locus downstream of a lox P flanked STOP cassette. These mice were crossed to mice with Cre-recombinase expression from the CD19 promoter, leading to hnRNPLL expression early in B cell development with the expected effect on CD45 alternative splicing. However, we were unable to observe a significant effect on B cell development. We further generated mice for Cre-recombinase mediated hnRNPLL deletion. Similar to the CD19 knockin mice, deletion of hnRNPLL in B cells of CD19-Cre mice did not impact B cell development. Preliminary data suggested that deletion of hnRNPLL in T cells of Lck-Cre mice perturbs early thymic development, but these results were not reproducible. As a detailed analysis of immune regulation is outside the current focus of the laboratory, we are in the process of identifying researchers to whom we can transfer these transgenic strains. In addition, the knockout and knockin strains will be subjected to cryopreservation.